Descriptions

Surface and subsurface data indicate that Cretaceous strata
in the southern Ventura basin are part of the northward prograding
Chatsworth submarine fan. The fan extends westward as far as
Trancas Beach in the Santa Monica Mountains and wells in the
Oxnard Plain and on Oak Ridge. The eastern edge of the fan is
constrained by wells in western San Fernando Valley which contain
fine-grained strata which may have been deposited east of the
Chatsworth fan. The Nonmarine Simi Conglomerate overlies the
Cretaceous and is itself overlain by Paleocene marine beach sandstone
and siltstone. These marine strata do not extend eastward
into the San Fernando Valley. The lower Paleocene and Cretaceous
strata were overlapped by the upper Paleocene Santa Susar1a and
middle Eocene Liajas Formations. Sedimentation patterns for the
Santa Susana and Llajas may be explained by two models: (1) A
northwest-trending submarine ridge on which muds and silts were
deposited, was flanked on the northeast and southwest by troughs
receiving deep-water sands. (2) Both formations were deposited
on a southwest-facing shelf, slope, and turbidite trough. Subsurface
data important in basin analysis include 1) bathyal paleo-
bathymetry for the entire Santa Susana, 2) sand channels in the
Santa Susana which possibly funneled sediment westward down a
submarine slope, 3) shelf-facies(?) Eocene strata with neritic
to upper bathyal paleobathymetry in Oxnard Plain, and 4) Llajas
fades in northern Simi Valley suggesting gradation upward from a
shallow marine to outer shelf or slope environment. Facies correlations
across the Simi fault indicate no large-scale post-
Paleogene strike-slip displacement. If these sequences were
rotated, as suggested by paleomagnetic data, the restored Cretaceous
fan would come from the east and the restored Paleocene shoreline
would face south. Thus paleogeography for the Cretaceous is
simplified by the rotation hypothesis, but Paleocene paleogeography
is made more complicated.